An embodiment of the invention is related to achieving power savings in electronic systems, such as mobile computing and communication products (e.g. notebook computers), having integrated circuits.
Power savings is an important part of operating an electronic system, not just for achieving energy conservation in general but also for extending the run-time of a battery-powered mobile product such as a notebook or laptop computer.
A typical notebook personal computer includes the following components. A battery is used as the main power supply of the computer. The battery supplies power to all of the different components of the computer including, for example, the display, the mass storage device, and computing logic. The computing logic typically includes a processor die and a system chipset, both of which are examples of integrated circuits. The chipset allows the processor to communicate with I/O devices and with main memory in the computer. Modern integrated circuits use relatively low, DC supply voltages on the order of about 1 Volt, to achieve lower power consumption. Since the output voltage of the main power supply can be substantially greater than the input supply voltage of integrated circuits, e.g. 10 Volts or more, a step down switching regulator is often used to provide this relatively low, well regulated DC voltage to the integrated circuits at power levels of 20 Watts and more.
A popular power saving technique implemented in notebook computers is to use integrated circuits that can operate in a state or mode of reduced work capability that leads to reduced power consumption. For example, some processors, such as the PENTIUM IV brand of processors by Intel Corp. of Santa Clara, Calif., can operate according to an internal core clock signal that can be on/off modulated. This is an example of processor clock ‘throttling’ which temporarily puts the processor in a non-active mode, which in turn significantly reduces processor power consumption. A broader set of power states or work capability modes have been defined to place the processor in various ‘sleep’ states. In a sleep state, some or all of the computing and I/O functions of the processor are essentially shut down, by either stopping a clock signal to them or reducing their supply voltage to a minimum level. This reduction in work capability causes a significant reduction in the load current of the switching regulator that supplies power to the processor.
Another way of reducing power consumption is suggested in U.S. Pat. No. 5,945,817 to Nguyen, where a narrower, rather than broader, range is maintained for the processor input supply voltage. That patent describes a variable voltage supply that is coupled to receive a power status signal from a processor, where this signal indicates a power consumption mode in which the processor operates. The voltage supply provides the processor with a supply voltage that is a function of the power status signal and that can be maintained in the narrower range to reduce the power consumption of the processor when the processor is idle.